The present invention relates to a quartz resonator and its support structure and more particularly to a hermetically sealed quartz resonator having a micro-machined support structure.
Quartz resonators are used for oscillators or sensing devices. In particular, a quartz resonator can be used as an oscillator for a watch or any other application which requires small size, low cost, and ruggedness. The quaratz resonator might also be used for microporcessor applications. A quartz resonator operates by resonating in response to a stimulus, which may be a physical event, such as acceleration or force or pressure, or an electrical signal. In the former usage, the resonator acts as a transducer, and in the latter case the resonator acts as a frequency source.
Previous technology for resonator support structures is varied and includes features which minimize the effects tending to restrict motion of the resonating surface resulting from physically holding the vibrating resonator body. To this end, the support is usually placed at a vibrational node of the resonator body. With discs operating in radial extension modes, attachment at the center of the disc is a conventional technique for support.
For shear mode type resonators with little vibrational motion normal to the plane of the resonator, conventional support techniques have included various elastic clamping means at the periphery of the resonator where relative shear-motion quiescence occurs. These clamps have conventionally been wires, metallic ribbons, metallic springs, etc. Another conventional support technique has been to fashion the resonator and the resonator support from a single piece of quartz by chemical or mechanical machining methods.
U.S. Pat. No. 4,362,961 to Gerber discloses an encapsulated piezoelectric resonator device wherein a vibrating member and a frame member are formed integrally on a single substrate. The frame/resonator member is sandwiched between and bonded to two cover members which are positioned above and below the resonator member, respectively. The resonator member is connected to a number of electrodes and connection to the electrodes is provided by passages through the two cover members. This resonator operates in a flexure mode. The resonator member and the cover members are rigidly fixed together.
U.S. Pat. No. 4,234,811 to Hishida et al. discloses a supporting structure for a thickness-shear type crystal oscillator for watches wherein the supporting structure of a resonator element has a pair of flexible tongues to support the resonator element from both the top and the bottom of the resonator element. Additionally, another set of tongues is provided to engage notches on the resonator element's periphery to prevent lateral motion.
U.S. Pat. No. 4,988,621 to Nakayama et al. discloses an insulating ring with projections for supporting and rigidly clamping a quartz resonator. Electrodes are placed directly onto the shear-mode resonator and small wires electrically connect the electrodes to the insulating ring.
U.S. Pat. No. 2,002,167 to Beckmann discloses a crystal quartz resonator wherein capacitive coupling is used to excite the resonator. A support for the resonator is disclosed which uses notches and pins on the edge of the resonator.
U.S. Pat. No. 2,161,980 to Runge et al. discloses an elastically oscillating oscillator which uses a "wave reflection" phenomenon to produce a superior support structure for a vibrating member. A capacitively coupled drive structure in an evacuated enclosure to reduce deleterious air damping is disclosed.
U.S. Pat. No. 4,445,256 to Huguenin et al. discloses a method for manufacturing piezoelectric resonator components wherein the resonator is produced using "wafer level assembly" wherein a multiplicity of resonators are formed on a large quartz wafer. This quartz wafer has been welded to a top and bottom cover which are ceramic or glass.
U.S. Pat. No. 4,764,244 to Chitty et al. and 4,831,304 to Dorey et al. disclose a method of making a resonator, such as a sensor, which uses micro-machining technology.